This story is a sequel to Aitran
Twilight and Rainbow are asked by Star Swirl the Bearded to take on the challenge of finding his lost wife and daughter in the decaying world of Sohndar, which is ruled by an old enemy of Star Swirl's family who has been trapped there for uncounted years. Although their adventures in the worlds of Aitran have given our heroes the confidence to succeed, they'll soon find that Sohndar is an entirely different bale of hay.
Image by Muffinsforever